Diabetes leads to myocardial dysfunction in the absence of coronary artery disease (CAD). This condition, diabetic cardiomyopathy (DCM), has been postulated to contribute to higher incidences of both congestive HF and mortality in diabetic patients. Even more serious is the occurrence, of HF following myocardial infarction (Ml) in long-standing diabetics, as diabetes induces adverse cardiac remodeling after Ml and leads to more severe HF. HF in diabetes with or without CAD (collectively referred to as diabetic HF) poses a major threat to public health as the incidence of diabetes rises, and as medical management prolongs the life span of diabetics. Despite these unique features of diabetic HF and the foreseen public health disaster due to the poor prognosis of diabetic HF, there have been no specific therapies targeting the principal pathophysiologic problems of diabetic heart diseases. We recently identified that impaired angiogenesis (formation of new vasculature from pre-existing mature endothelial cells) and decreased availability of circulating endothelial progenitor cells (EPCs) play a major role in the development of DCM. Recent identification of EPCs derived from adult bone marrow, which contribute to de novo development of vessels (vasculogenesis), has raised the possibility of utilizing these cells to repair ischemic/infarcted myocardium by inducing new vessel formation through the processes of vasculogenesis and angiogenesis. The long-term goal of this project is to define the role of the vasculature and its related biological factors in the development of diabetic HF and to establish more effective therapeutic strategies to treat diabetic HF. Accordingly, in this Proposal, we designed a series of experiments to investigate the role of angiogenesis and vasculogenesis in the development of diabetic HF and the impact of EPC transplantation on diabetic HF. In Specific Aim 1, we will investigate the role of defective myocardial angiogenesis and EPCs in the development of diabetic HF. In Specific Aim 2, we will explore the therapeutic impact of EPC transplantation on diabetic HF by using DCM and diabetic Ml models. In Specific Aim 3, we will investigate potential mechanisms which mediate the therapeutic effect of EPC transplantation. For this series of experiments, we will use streptozotocin-induced diabetic rat and mouse models and perform comprehensive functional, molecular and histopathologic examinations on the hearts and EPCs. We anticipate that the results of the experiments outlined in this proposal will yield new insight into the pathophysiologic features of diabetic HF and the application of innovative stem/progenitor cell therapy for repairing or preventing myocardial injury associated with diabetes. The successful completion of these studies should provide novel therapeutic strategies to address a clinical disorder that accounts for major morbidity and mortality and has to date been inadequately addressed by available clinical therapies.